Question

How many quarts of pure antifreeze must be added to 9 quarts of 30 % antifreeze solution to obtain a 50% antifreeze solution ?

Answer 1

Let

x -----> quarts of pure antifreeze

Remember that

30%=0.30

50%=0.50

so

x+9(0.30)=(x+9)(0.50)

solve for x

x+2.70=0.50x+4.50

x-0.50x=4.50-2.70

0.50x=1.8

x=3.6

therefore

The answer is 3.6 quarts